Use file magic to determine file type, not file extension.

Bug: 10614658
Change-Id: I9156dfca78ac8cd1c62fb258825cc791629270a4
diff --git a/runtime/oat.h b/runtime/oat.h
index a5c6bed..a653cf8 100644
--- a/runtime/oat.h
+++ b/runtime/oat.h
@@ -27,6 +27,9 @@
 
 class PACKED(4) OatHeader {
  public:
+  static const uint8_t kOatMagic[4];
+  static const uint8_t kOatVersion[4];
+
   OatHeader();
   OatHeader(InstructionSet instruction_set,
             const std::vector<const DexFile*>* dex_files,
@@ -78,9 +81,6 @@
   std::string GetImageFileLocation() const;
 
  private:
-  static const uint8_t kOatMagic[4];
-  static const uint8_t kOatVersion[4];
-
   uint8_t magic_[4];
   uint8_t version_[4];
   uint32_t adler32_checksum_;